Exposing PseudoAstronomy

October 16, 2012

Podcast #53: Lunar Formation and Origins

This was a listener-requested episode, how the moon formed. There isn’t too much pseudoscience in this one, though a few references are made to misconceptions in Mike Bara’s new book. And some misunderstandings by Bob Novella from episode 350 of The Skeptics’ Guide to the Universe podcast.

Since I was trying to get this episode out quickly, several of the normal segments are not present, but I did have a bit of another run-in with David Nabhan, the very “passionate” guy from episode 50 on lunatic earthquakes. If you have maybe 10-15 minutes to kill, I highly recommend reading the exchange starting part-way down that thread on October 4.


  1. Whoa, D. Nabhan seems to have missed the point that he was a peripheral topic in your Episode 50, but he seems to be more than willing to brag as if he were the principle subject of your talk. I truly wish he would present some data, instead of criticizing so many trivial points, and lying about what he said, in order to distract everyone from noticing he has nothing to back up his claims. He seems more than willing to argue forever, if that gets more people interested in reading his book, so he can make more money. My cynical side wants to say he’s running low on cash, so he’s using this opportunity to make some more.

    And I noticed Mike Bara chimed in, even if all he was doing was egging Nabhan on. I guess he was hoping Nabhan would take you down a peg or two. Didn’t happen…

    Comment by Rick K. — October 16, 2012 @ 4:06 pm | Reply

    • That wasn’t Mike, if you’re talking about the CoastGab post. It’s some guy who put Mike as his avatar for whatever reason, likely to mock him. If you poke around that forum, you’ll see a lot of … interesting … avatars. And in the long Hoagland thread, the number of … interesting … Photoshop jobs is … interesting.

      Comment by Stuart Robbins — October 16, 2012 @ 6:05 pm | Reply

  2. Ah, okay. Didn’t know folks were using avatars like that. No big deal. It was fun reading through David Nabhan’s posts on CoastGab. His first post’s second paragraph was chocked full of logical fallacies, and his subsequent posts kept up the trend. It was good exercise, going through and finding every one of them.

    I still can’t understand why he feels he is owed a warning when somebody publicly talks about him. Should I have contacted him first, before I posted this entry, so he’d have a chance to defend himself?

    Comment by Rick K. — October 17, 2012 @ 7:58 am | Reply

    • Yeah, I’m “fine” with his crappy science analysis (or it may be fine, and mine may be wrong, but he won’t share).

      It’s the entitlement issue. And the “you should all call the governor regardless” stuff. I was one class away from a psych minor … in my opinion as the medical professional I don’t play in any context, he strikes me as an egomaniac with some small delusions of grandeur. Or, perhaps just an attention-whore, without meaning to disparage persons who sell sex.

      Comment by Stuart Robbins — October 17, 2012 @ 11:05 am | Reply

      • I don’t have any creds to back me up, so all I have is my personal opinion. My guess is his book sales are down, so he’s trying to drum up more. Any publicity is helpful, even if it gets people curious enough to buy his books to see where he’s coming from. In our modern media, “he-said, she-said” environment, it’s very easy for someone to get into the habit of expecting to be listened to, as long as one’s position is controversial.

        I find George Noory too credible by half, and he constantly asks leading questions of his “guests”, which can lead into all sorts of irrelevant speculation. His recent talk with Mike Bara was a good example of that, with Mr. Noory offering all sorts of stuff that had nothing to do with Mr. Bara’s topic, forcing the latter to respond with nonsense. If anything, it made Mr. Bara seem just as credulous, if not more so.

        Comment by Rick K. — October 18, 2012 @ 6:53 am

  3. The interesting thing about the current “big splash” or giant impact theory of the moon’s formation is that, in a way, it incorporates elements of all three previous theories.

    Co-formation: Theia, the hypothetical impactor, did co-form with the earth in the same solar orbit, most likely at one of the two stable Lagrange points L4 or L5. They just didn’t co-form around a common center of mass.

    Capture: Earth did “capture” Theia in the sense that it impacted. That’s certainly one way to remove a lot of excess energy without the help of a third body.

    Fission: After Theia’s impact Earth did fission off what became the moon.

    What clinches it for me is the fact that the L4/L5 points are stable only when the object is below a certain mass. When Theia originally formed, its position was stable but as it continued to accrete and gain mass above about 10% of earth’s mass, it began to oscillate around the Lagrange point until it eventually swung so far that it hit the earth.

    I take minor exception to your characterization of angular momentum as a form of energy. They’re quite distinct, with different units of measurement.

    They’re also different in an important practical way. Although both mass/energy and angular momentum are conserved quantities, energy (kinetic or potential) can easily be converted in large amounts to heat and dissipated by radiation to space; angular momentum cannot. Only very slow mechanisms like the Yarkovsky effect can do this, again via radiation to space, and it’s significant only for small bodies over long periods of time.

    The dissipation of energy but not angular momentum is very important to understanding the behavior of rotating bodies in space. Rotating asymmetric objects with *any* internal mechanism for dissipating energy (essentially every real object, no matter how seemingly rigid) always end up spinning around the axis with the greatest moment of inertia because this is the state that minimizes kinetic energy while conserving the original angular momentum.

    Comment by Phil — October 18, 2012 @ 7:38 pm | Reply

  4. Another minor nit: KREEP stands for Potassium, Rare Earth Elements and Phosphorus, not Potassium.

    Comment by Phil — October 18, 2012 @ 8:15 pm | Reply

  5. Oh, speaking of co-formation and the puzzle of the oxygen isotope ratios being the same on the earth and the moon, it’s my understanding that the planets have different isotope ratios because various subtle mass-dependent mechanisms separated them in the original proto-solar-system nebula. So how likely is it that Theia and Earth would have had the same isotope ratios because they formed in a common orbit from the same set of planetesimals at the same distance from the sun?

    Comment by Phil — October 18, 2012 @ 10:01 pm | Reply

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